1. Field of the Invention
The present invention relates to an imprinting stamper and a method of manufacturing the same.
2. Description of Related Art
In the known process of manufacturing semiconductor devices, photolithographic technology has often been used to form a microscopic pattern. While the tendency toward microscopic patterns grows, this approach has a problem that pattern sizes are restricted by the wavelength of light used for exposure and higher positioning accuracy is required, resulting in higher equipment cost. On the other hand, as technology for high precision patterning at low cost, nano-imprint technology has been known in which a specific desired pattern is transferred to a resist film layer formed on a substrate surface by stamping with a stamper with the same convexo-concave pattern as the desired pattern.
FIGS. 5A to 5F schematically show an example of the process of forming a microscopic pattern using nano-imprint technology. In this example, as shown in FIG. 5A, a substrate 503 coated with patterning resin 502 as a medium on which a transfer is made, and a mold 501 are fixed on a stage (not shown) which can control the distance between them. Next, as shown in FIG. 5B, the convexo-concave pattern of the mold 501 is transferred to the resin 502 by moving the stage and pressing the mold 501 against the resin 502. At this moment, resin remains in the concave parts of the resin 502. The remaining resin in the concave parts is removed by anisotropic reactive ion etching (RIE) or a similar technique until the pattern concave parts of the substrate 503 are exposed. The resin pattern thus created may be used as follows. For example, after etching the exposed parts of the substrate 503 as shown in FIG. 5C, grooves as shown in FIG. 5D can be made by removing the resin 502. Another possible example is that after a metal layer 504 is formed on the entire surface of the transfer medium as shown in FIG. 5E, the resin 502 is removed to make a structure with a specific pattern as shown in FIG. 5F.
This nano-imprint technology has a problem that the existence of micron-order waves on the stamper or substrate surface may hamper high precision transfer of a microscopic pattern. One possible solution to this problem is that an elastomer layer is made on the backside of the stamper to distribute the imprinting pressure evenly to enable the stamper to accommodate the wavy surface of the substrate (for example, see Patent Document 1).
Patent Document 1: Japanese Patent Laid-open No. 2005-183985 (US 2005/0133954 A1)
The elastomer layer on the backside of the stamper as described in Patent Document 1 makes it possible to transfer a microscopic pattern while accommodating a wavy surface of the stamper or substrate. However, some substrates locally have foreign bodies or projections of 2-10 μm in diameter and/or height. The stamper of a hard material with an elastomer layer on its backside as described above cannot accommodate such local projections, resulting in an imperfect pattern or a transfer defect where some part of the pattern is missing in the transfer made.
Besides, in a convexo-concave pattern formed by nano-imprint technology, resin film (remaining film) is left beneath concave parts. In order to use this convexo-concave pattern as a mask in processing a substrate, the remaining film is removed because it is unwanted. For a higher substrate processing accuracy, the thickness of the remaining film must be decreased to several dozen nanometers or less. In creation of a pattern with a thin remaining film, the above problem of local projections is more serious. Therefore, in the imprint technology for forming microscopic patterns with high accuracy, if a stamper made of a hard material such as silicon, quartz or metal should be used as in the past, it would be unavoidable to produce imperfectly transferred pattern areas on a projection-bearing substrate.
The present invention has been made in view of the above problem and has an object to provide a stamper which accommodates local projections of a substrate and does not cause transfer defects.